Matrix metalloproteinases MMP-2, MMP-7 and MMP-9 in denervated human muscle.

Proteolytic enzyme expression was studied by matrix metalloproteinases (MMP) immunoreactivity (-IR) in muscle biopsies from patients with amyotrophic lateral sclerosis (ALS), spinal muscle atrophy (SMA) and chronic axonal neuropathies (CANP). In normal muscle MMP-2-, MMP-7-, and MMP-9-IR was localized at neuromuscular junctions, in vessels and nerve branches. ALS biopsies of clinically non-affected muscles revealed neither MMP-2, -7-IR nor MMP-9-IR in atrophied myofibers. ALS-affected biopsies revealed MMP-9-IR, and to lesser extent MMP-2- and MMP-7-IR at normal sized and atrophied myofibers. Biopsies of SMA showed MMP-9- and MMP-7-IR at normal sized and atrophic myofibers, while MMP-2-IR was undetectable. In CANP MMP-9-IR was found at normal sized and atrophied myofibers. Distinct expression patterns of MMPs may thus reflect different stages of muscle denervation atrophy.     

Prediction of response to IVIg treatment in patients with lower motor neurone disorders

The distinction between multifocal motor neuropathy, treatable by intravenous immunoglobulins (IVIg), and degenerative motor neurone disorders is often difficult. To find predictive factors for the response to IVIg treatment, 40 consecutive patients with pure lower motor neurone disorders (LMND) were prospectively examined. They all received at least two times IVIg (2 g/kg bodyweight). Prior to the first and before all the following treatments a standardized evaluation was performed including clinical examination, neurophysiological and laboratory evaluation. According to changes in the neurological examination and the Neuromuscular Symptom Score, the patients were divided into responders and non-responders after the second course of treatment. In our study, no single clinical, neurophysiological, or laboratory parameter was sensitive enough to predict response. The only single parameter that highly correlated with a positive response to treatment was an elevated GM1 antibody titre. Lack of response to IVIg treatment is likely in patients with generalization of electromyographic signs of denervation beyond the clinically involved site, proximal localization of the weakness, and an elevated level of the creatinekinase. Conduction blocks do not distinguish between both groups. We propose a scoring system combining clinical, serological and neurophysiological data in order to decide which patients with LMND may receive IVIg.     

Lipidsenker- und andere toxische Myopathien

A growing number of therapeutic agents and exogenous toxins are harmful to structure and function of human skeletal muscle. The clinical syndrome encompasses asymptomatic creatine kinase elevation, myalgia, exercise intolerance, muscle paresis and atrophy, and lastly acute rhabdomyolysis. Toxic myopathies are potentially reversible, hence a prompt recognition is particularly helpful for the early diagnosis and in conclusion elimination of a myopathy inducing toxin. Toxic myopathies may be classified as acute or chronic accordingly to the exposition time to a toxin. Main source of an exogenous induced toxic myopathy is chronic alcohol abuse. Alcohol excess induces acute and/or chronic neuropathy and myopathy, consequently muscle wasting and weakness occurs. Drug-induced myopathies are most frequently seen due to amplified utilization of corticosteroids or lipid lowering agents.     

Novel missense mutation in the caveolin-3 gene in a Belgian family with rippling muscle disease

Rippling muscle disease (RMD) is a rare muscle disorder characterised by muscle stiffness, exercise induced myalgia, and cramp-like sensations. It is genetically heterogeneous and can be acquired, but most cases show autosomal dominant inheritance due to mutations in the caveolin-3 (CAV3) gene. We report a novel heterozygous missense mutation in CAV3 in a Belgian family with autosomal dominant RMD. A 40 year old woman complained of fatigue, exercise induced muscle pain, and muscle cramps since the age of 35. Neurological examination revealed percussion induced rapid muscle contractions (PIRCs) and localised muscle mounding on percussion; muscle rippling was not observed. Creatine kinase (CK) was elevated but electromyography and nerve conduction studies were normal. Fluorescence immunohistochemistry revealed reduced caveolin-3 and dysferlin staining in a quadriceps muscle biopsy. Western blot analysis confirmed severely reduced caveolin-3 levels, whereas dysferlin was normal. Sequence analysis of the two coding exons of CAV3 revealed a hitherto unreported heterozygous C82A transversion in the first exon, predicting a Pro28Thr amino acid exchange. Thr patient's first degree relatives did not present with neuromuscular complaints, but PIRCs, muscle mounding, and muscle rippling were found in the mother, who also carried the CAV3 mutation.     

A sporadic case of rippling muscle disease caused by a de novo caveolin-3 mutation.

OBJECTIVE: To determine the cause of sporadic rippling muscle disease (RMD) in a 24-year-old patient. BACKGROUND: RMD is a rare myopathy characterized by percussion-induced rapid muscle contractions (PIRC), muscle mounding, and rippling waves. We have recently found that autosomal dominant RMD is caused by mutations in the caveolin-3 gene (CAV3) on chromosome 3p25. Possibly, increased activity of neuronal nitric oxide synthase (nNOS) contributes to the clinical characteristics of increased mechanical muscle hyperexcitability. METHODS: Clinical examination, mutational analysis, and immunohistochemistry of muscle tissue were performed in a patient with sporadic RMD. RESULTS: The authors observed a de novo CAV3 missense mutation Arg26Gln. Immunohistochemistry showed reduced caveolin-3 surface expression in a muscle biopsy. In addition, the authors found normal sarcolemmal nNOS expression and a reduced expression of alpha-dystroglycan in muscle fibers. CONCLUSIONS: These data confirm that RMD is caused by CAV3 mutations. Moreover, there is evidence that CAV3 mutations may also be found in patients without a positive family history of RMD.     

Proteomic characterization of aggregate components in an intrafamilial variable FHL1-associated myopathy

Myopathies associated with mutations in FHL1 are rare X-linked dominant myofibrillar myopathies. By clinical examination, histopathology, Sanger sequencing, and laser microdissection combined with quantitative mass spectrometry, we were able to identify the causative gene mutation and protein aggregate composition in two brothers with a late-onset X-linked scapulo-axio-peroneal myopathy. The severely progressive course of the disease revealed a remarkable intrafamilial variability of the clinical presentation. Protein aggregation and reducing bodies were observed in the muscle biopsy. Using quantitative mass spectrometry we identified the FHL1 protein as the component showing highest increased abundance in the aggregates in both patients, however strikingly in a different absolute amount in both brothers. Furthermore, we identified the causative C224W mutation in the fourth LIM-domain of FHL1 in both. Thus, of note is the striking evidence of reducing bodies in the muscle biopsy in both adults, and our proteomic data confirm the underlying gene defect with an intrafamilial variability by the ratio of the total protein content in the aggregates. We suggest that our combined approach has a high potential as a new tool for identification of causative gene mutations and raises hints on possibly intrafamilial variability in protein aggregation disorders. As all clinical subtypes and mutations in each exon of the FHL1 gene are associated with myofibrillar alterations and reducing bodies, we would like to suggest terming the whole group as FHL1-associated myopathies.     

Age effects on interleukin-6 and interleukin-1beta responses to endurance exercise in patients with neuromuscular diseases

Plasma IL-6 before and 20 min after prolonged muscular exercise for 20 min at the individual aerobic/anaerobic threshold was analyzed in patients with neuromuscular diseases and in controls. Patients were assigned to the following diagnostic categories: Controls (n=18); amyotrophic lateral sclerosis (n=7); peripheral neuropathy (n=6); muscular dystrophy (n=13); mitochondriopathy (n=3); myopathy (others) (n=3); inflammatory myopathy (n=6); mononeuropathy (n=4). The concentrations of IL-6 before exercise were 5.55+/-0.94 pg/ml, and 6.52+/-0.97 pg/ml after exercise (P=0.0001). We introduced the independent variables age, sex and diagnostic category into a stepwise multiple linear regression model. Age emerged as a significant predictor of the IL-6 ratio (IL-6 post exercise/lL-6 before exercise). The regression equation was: IL-6 ratio=0.87+0.009xage (years), R=0.33, P<0.01, simple linear regression model. All IL-1beta concentrations were below the sensitivity of the assay (5 pg/ml). Concerning patients with neuromuscular diseases, the age associated increased IL-6 release after exercise could mean additional muscle damage.